create or replace trigger "BI_STDT_EXAM_RESULTS"   
  before insert on "STDT_EXAM_RESULTS"               
  for each row  
begin   
  if :NEW."RESULT_ID" is null then 
    select "STDT_EXAM_RESULTS_SEQ".nextval into :NEW."RESULT_ID" from sys.dual; 
  end if; 
end; 
/